linux-kernel - [[PATCH v2] 1/1] kprobes: retry pending optprobe after freeing blocker

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Message-ID: <2D68B83E59A24077+20251030093644.430507-1-hongao@uniontech.com>
Date: Thu, 30 Oct 2025 17:36:44 +0800
From: hongao <hongao@...ontech.com>
To: mhiramat@...nel.org
Cc: naveen@...nel.org,
	anil.s.keshavamurthy@...el.com,
	davem@...emloft.net,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org,
	hongao <hongao@...ontech.com>
Subject: [[PATCH v2] 1/1] kprobes: retry pending optprobe after freeing blocker

Thanks for the review.

The freeing_list cleanup now retries optimizing any sibling probe that was
deferred while this aggregator was being torn down.  Track the pending
address in struct optimized_kprobe so __disarm_kprobe() can defer the
retry until kprobe_optimizer() finishes disarming.

Signed-off-by: hongao <hongao@...ontech.com>
---
Changes since v1:
- Replace `kprobe_opcode_t *pending_reopt_addr` with `bool reopt_unblocked_probes`
  in `struct optimized_kprobe` to avoid storing an address and simplify logic.
- Use `op->kp.addr` when looking up the sibling optimized probe instead of
  keeping a separate stored address.
- Defer re-optimization by setting/clearing `op->reopt_unblocked_probes` in
  `__disarm_kprobe()` / consuming it in `do_free_cleaned_kprobes()` so the
  retry runs after the worker finishes disarming.
---
 include/linux/kprobes.h |  1 +
 kernel/kprobes.c        | 28 ++++++++++++++++++++++------
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 8c4f3bb24..4f49925a4 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -338,6 +338,7 @@ DEFINE_INSN_CACHE_OPS(insn);
 struct optimized_kprobe {
 	struct kprobe kp;
 	struct list_head list;	/* list for optimizing queue */
+	bool reopt_unblocked_probes;
 	struct arch_optimized_insn optinsn;
 };
 
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index da59c68df..799542dff 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -514,6 +514,7 @@ static LIST_HEAD(freeing_list);
 
 static void kprobe_optimizer(struct work_struct *work);
 static DECLARE_DELAYED_WORK(optimizing_work, kprobe_optimizer);
+static void optimize_kprobe(struct kprobe *p);
 #define OPTIMIZE_DELAY 5
 
 /*
@@ -591,6 +592,21 @@ static void do_free_cleaned_kprobes(void)
 			 */
 			continue;
 		}
+		if (op->reopt_unblocked_probes) {
+			struct kprobe *unblocked;
+
+			/*
+			 * The aggregator was holding back another probe while it sat on the
+			 * unoptimizing/freeing lists.  Now that the aggregator has been fully
+			 * reverted we can safely retry the optimization of that sibling.
+			 */
+
+			unblocked = get_optimized_kprobe(op->kp.addr);
+			if (unlikely(unblocked))
+				optimize_kprobe(unblocked);
+			op->reopt_unblocked_probes = false;
+		}
+
 		free_aggr_kprobe(&op->kp);
 	}
 }
@@ -1009,13 +1025,13 @@ static void __disarm_kprobe(struct kprobe *p, bool reopt)
 		_p = get_optimized_kprobe(p->addr);
 		if (unlikely(_p) && reopt)
 			optimize_kprobe(_p);
+	} else if (reopt && kprobe_aggrprobe(p)) {
+		struct optimized_kprobe *op =
+			container_of(p, struct optimized_kprobe, kp);
+
+		/* Defer the re-optimization until the worker finishes disarming. */
+		op->reopt_unblocked_probes = true;
 	}
-	/*
-	 * TODO: Since unoptimization and real disarming will be done by
-	 * the worker thread, we can not check whether another probe are
-	 * unoptimized because of this probe here. It should be re-optimized
-	 * by the worker thread.
-	 */
 }
 
 #else /* !CONFIG_OPTPROBES */
-- 
2.47.2